Protein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution
Title | Protein Flexibility and Synergy of HMG Domains Underlie U-Turn Bending of DNA by TFAM in Solution |
Publication Type | Journal Article |
Year of Publication | 2018 |
Authors | Rubio-Cosials, Anna, Battistini Federica, Gansen Alexander, Cuppari Anna, Bernadó Pau, Orozco Modesto, Langowski Jörg, Tóth Katalin, and Solà Maria |
Journal | Biophysical Journal |
Volume | 114 |
Pagination | 2386 - 2396 |
Date Published | 05/2018 |
ISSN | 0006-3495 |
Abstract | Human mitochondrial transcription factor A (TFAM) distorts DNA into a U-turn, as shown by crystallographic studies. The relevance of this U-turn is associated with transcription initiation at the mitochondrial light strand promoter (LSP). However, it has not been yet discerned whether a tight U-turn or an alternative conformation, such as a V-shape, is formed in solution. Here, single-molecule FRET experiments on freely diffusing TFAM/LSP complexes containing different DNA lengths show that a DNA U-turn is induced by progressive and cooperative binding of the two TFAM HMG-box domains and the linker between them. SAXS studies further show compaction of the protein upon complex formation. Finally, molecular dynamics simulations reveal that TFAM/LSP complexes are dynamic entities, and the HMG boxes induce the U-turn against the tendency of the DNA to adopt a straighter conformation. This tension is resolved by reversible unfolding of the linker, which is a singular mechanism that allows a flexible protein to stabilize a tight bending of DNA. |
URL | https://www.sciencedirect.com/science/article/pii/S0006349517349755 |
DOI | 10.1016/j.bpj.2017.11.3743 |